Comparator amplifier

ABSTRACT

A pair of substantially opposed nozzles issue respective input fluid streams along a common wall extending from a sidewall of each of the nozzles. A wedge shaped protrusion is formed in the wall approximately midway between the nozzles, the protrusion serving to impart a velocity component normal to the wall to each of the input streams. The streams interact in the region of the protrusion producing a resultant stream having an angular direction with respect to the wall which depends upon the pressure differential between the two input streams. Alternatively the resultant stream may be deflected by control stream to represent a measure of control stream strength.

7 United States Patent Inventors Appl. No.

l-iled Patented Assignee Peter Bauer Germantown, Md.; Robert N. Jones,Wallingi'ord, Conn. 714,683

Mar. 20, 1968 Jan. 12, 1971 Bowles Engineering Corporation SilverSpring, Md.

a corporation of Maryland COMPARATOR AMPLIFIER 20 Claims, 3 DrawingFigs.

Int. Cl. Field of Search UNITED STATES PATENTS 3/1966 Bowles 137/s1.sFlSc 1/14 137/8l.5

References Cited 3,277,915 10/1966 Dockery 137/8l.5 3,366,131 1/1968Swartz 137/8l.5 3,435,837 4/1969 Sher 137/81.5 3,444,876 5/1969 Sierackiet a1. 137/81.5

Primary Examiner-Samuel Scott Attorney-l-lurvitz, Rose & GreeneABSTRACT: A pair of'subs tantially opposed nozzles issue respectiveinput fluid streams along a common wall extending from a sidewall ofeach of the nozzles. A wedge shaped protrusion is formed in the wallapproximately midway between the nozzles, the protrusion serving toimpart a velocity component normal to the wall to each of the inputstreams. The streams interact in the region of the protrusion producinga resultant stream having an angular direction with respect to the wallwhich depends upon the pressure differential between the two inputstreams. Alternatively the resultant stream may be deflected by controlstream to represent a measure of control stream strength.

PATENITEUJAN 1 2 m INVENTORS PETER BAUER 6n ROBERT M J ones )fl/wATTORNEYS g g m:

E x mm mm J x mm l p fin. g M T m 00 q i A v 5:31:5 )w/ mm i w M v 3 a Iv COMPARATOR AMPLIFIER BACKGROUND or THE INVENTION power stream of fluidrelative to an output passage. Where pressure is the parameter'beingamplified, the width of the output passage is made small relativeto thewidth of the power stream and the transverse portion of the power streamreceived by the output passage is dependent upon the relative moment ofthe control and power streams. The gain is equal to the change in outputpressure divided by the change in control stream pressure producing theoutput measure change. It is readily seen therefore that for a givenamplifier configuration the transverse pressure gradient of the powerstream is a limiting factor with respect to pressure gain of theamplifier since it is this pressure gradientwhich determines thepressure of the fluid received at the output passage'for a given powerstream deflection. The limitation on gain imposed by the power streamtransverse pressure gradient is often a severe disadvantage where highgain applications are involved.

Another characteristic of the stream interaction type pure fluidamplifier which limits its use in certain applications is its somewhatlimited dynamic operating range. Specifically, where control streams ofhigh pressure levels are to be employed, correspondingly high powerstream pressures are required in order that the amplifier not be tooreadily saturated. Where both the control stream pressure and powerstream pressure are relatively high, sensitivity to low level pressurechanges in the control signal decreases correspondingly.Moreover,increasing power stream pressure beyond a predetermined level tendsto-produce power stream turbulence which results in nonlinearities inthe'amplifier gain characteristic. 7

Another prior art pure fluid amplifier is the turbulence amplifier, anexample of which may-be found in US. Pat. No. 3,234,955 to Anger. In theturbulence amplifier a normally laminar power stream is received at anoutput passage, the power stream being rendered selectively turbulent asa function of a control stream directed to intercept the power stream.The pressure level of the control stream must be maintained sufficientlylow as to avoid deflection of the power stream but sufficiently highsoas'to produce turbulence effects at the output passage which aremonitorable. his clear that the dynamic operating range of inputpressures for the turbulence amplifier is severely limited.

bient conditions with ,the result that hysteresis effects are producedin the output signal pressure as a function of the differential inputpressures. Further, the devices are quite noisy.

It is an object of the present invention to provide a single pure fluidamplifier which is substantially devoid of the abovedescribeddisadvantages inherent in prior art pure fluid amplifiers.

It is another objectv of the present invention to provide a compact purefluid amplifier having a relatively high gain. large dynamic operatingrange of pressures, and high-pressure recovery characteristics ascompared with prior art pure fluid amplifiers.

Another problem with prior artpure fluid amplifiers concerns deviceshaving one or more stable conditions. Specifically, the boundary layertype pure fluid amplifier employs the boundary layer lock-on phenomenonwherein a power stream is caused to lock-on to one or the other of apair of sidewalls of a chamber or output passage, the power stream beingdirected to an appropriate output passage as afuriction of the wall orwalls to which it is attached. In order-for the power stream to beswitched from its position of lock-'on to'a sidewall, the force requiredto provide such switching (for example as provided by a control streaminteracting with the power stream) must be large enough not only todeflect the power stream itself, but also to overcome the lock-on forcesresulting from the boundary layer lock-on phenomenon. The switchingsensitivity of such a device is therefore inherently relatively low.

It is another objectof the present invention to provide a switching-typepure fluid amplifier which has inherently greater switching sensitivitythan prior art pure fluid devices.

SUMMARY OF THE INVENTION into theinteraction region from thewall so asto impart transverse velocity components to each input stream andconstraining the streams to interact in the immediate vicinity of thewedge rather than at some variable location transversely thereof. Theinteraction of the input streams produces a flow or pressure outputsignal as a function of the relative strength'of the input streams. Asdescribed in the referenced Bjornsen patent, the impact modulatorapproach does tend to .provide relatively high gain as a function ofchanges in input pressure differential, and its dynamicoperating rangeof input pressures is relatively large. However, there are a number ofdisadvantages inherent in the conventional impact modulator approachwhich render it unsuitable for many applications.

Specifically, the impacting streams create a region of equilibrium orzero dynamic pressure at a location which is dependent upon the relativestrengths of the streams, this location being variable as the inputstreamparameters vary. In-

order that a relatively large dynamic operating range of input pressuresbe accommodated, a relatively large device must beresultant force powerstream configuration or theinter'acting resultant stream which iseffectively pivoted about the protrusion and has a directiondepending-upon the relative momenta of the two input streams. One ormore output passages are disposed at the downstream end of theinteraction region to receive the resultant stream as a function of theinput pressure differential.

In another aspect of the present invention, the abovedescribed amplifierhas-both input nozzles connected toka common pressure source. Theresultant streammay-thenbe considered a power stream'which can bedeflectedbycontrol streams from additionally provided control nozzles asis conventionally done in stream interactiontype pure fluid amplifiers.However, the resultant-power stream in thepresent configuration isinherently more sensitive to deflectiortby control streams than thepower stream in conventional =pure fluidamplifiersfor thereason that thepower stream of the present invention is a resultant stream establishedin a balanced force system. A very slight unbalance in-the system, suchas will be provided by an additional control stream provides relativelylarge power stream deflection in responseito'a control stream signal. Inconventional pure fluid amplifiers, on

the other hand, the power stream is not a-resultant of balanced forces,but rather a stream having substantially only unidirectional components.

Eitherof the configurations discussed above, namely the input signalconfiguration may be readily employed as'either an analogue or switchingpure fluid device. Theresultant output stream in both configurations isproportional to the sum of the forces applied to the unit, andappropriate numbers of output passages can be positioned in accordancewith a desired operational mode for the amplifier.

BRIEF DESCRIPTION OF THE DRAWINGS The above and still further objects,features and advantages of the present invention will become apparentupon consideration of the following detailed description of one specificembodiment thereof, especially when taken in conjunction with theaccompanying drawing, wherein:

FIG. 1 is a plan view of one embodiment of the pure fluid amplifier ofthe present invention;

FIG. 2 is a plan view of a second embodiment of the pure fluid amplifierof the present invention; and

FIG. 3 is a block diagram of an analogto-digita'l converter utilizingthe amplifier illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of theaccompanying drawings, there is illustrated a pure fluid amplifierconstructed in accordance with the principles of the present invention.The cavities, passages, and noules comprising pure fluid amplifier 10may be formed in a flat plate 11 which may be covered by flat plate 12,the two plates being sealed in fluid-tight relationship and beingillustrated as composed of a clear plastic material for purposes offacilitating an understanding of the present invention. It should beunderstood, however, that other forms of fabrication may be employed andthat any material compatible with the working fluid employed may be usedin the construction of the amplifier 10.

Amplifier 10 comprises a pair of substantially opposed input nozzles 13and 15 communicating with an interaction chamber or region 17. Thedownstream end of chamber 17 is defined by a wall 19 formed by extendinga sidewall of each of nozzles 13 and 15 into chamber 17. As viewed inFIG. 1, the lower sidewalls of the two input nozzles 13 and 15 areextended to form the wall 19. Five fluid passages 21, 23, 25, 27, and 29communicate with chamber 17 in respective clockwise positions positionsbetween input nozzles 13 and 14 15 as viewed in FIG. 1. Although theinventive concept disclosed herein should not be construed as solimited, amplifier 10 is constructed symmetrically about itslongitudinal centerline which extends longitudinally through passage 25.Thus input nozzles 13, 15 and passage pairs 21, 29 and 23, 27 aresymmetrically disposed about passage 25.

A small wedge-shaped protrusion 31 extends from wall 19 into interactionregion 17. Protrusion 31 is positioned symmetrically about thelongitudinal centerline of the amplifier 10 and extends sufficientlyinto chamber 17 as to impart flow components to streams issued bynozzles 13 and 15 which are perpendicular at least to normal flow fromthese nozzles. It has been found that the protrusion 31 would be smallerthan the width of input nozzles 13 and 15 if gain (that is, deflectionchanges of the resultant stream as a function of changes in relativeinput pressure) is the important consideration; however, it isconceivable that the protrusions may be extended further into theinteraction chamber where other considerations, such as pressurerecovery, are paramount.

In one mode of operation the amplifier 10 of FIG. 1 may be provided withthe following connections: nozzles 13 and 15 are connected todifferentially varying input pressure sources; passages 21 and 29 arevented to ambient pressure; passages 23 and 27 are connected to autilization, measuring or indicating device; and passage is vented toambient pressure. It is to be understood that these connections are fora particular operational mode of amplifier l0, and that one or more ofpassages 21, 29 and 25 may serve as additional output passages. Inoperation, protrusion 31 deflects the input streams issued by inputnoules l3 and 15 proportionally in accordance with their pressures. Theamount of deflection to be imparted by the protrusion for a given inputpressure depends on the downstream configuration of amplifier 10, namelythe side of interaction chamber 17, the widths of the various passages,etc., and protrusion 31 is proportioned accordingly. Protrusion 31assures that both streams interact immediately in the vicinity of theprotrusion rather than on either side of it as the pressure differentialacross noules 13 and 15 varies. The interaction of the input streamsproduces a resultant stream which depends for its direction on thedifference in momenta of the two input streams, the resultant streameffectively originating at protrusion 31 so as to be pivoted about theprotrusion as a function of input pressure changes. When the pressuresat nozzles 13 and 15 are equal, since the amplifier 10 is symmetricalabout its center line, the net interacting forces of the two streamsbalance and the resultant stream is directed through passage 25 which,in the example described above, is vented to ambient pressure. As theinput presure differential changes the resultant stream is rotated aboutprotrusion 31 accordingly so that output passages 23 and 27 receivecorrespondingly more or less of the stream.

The direction of the resultant stream is extremely sensitive to changesin the input pressure differential. The reason for this is that a forcebalance system is quite sensitive to any force change in the system.Consequently a system in equilibrium is very sensitive to even a slightunbalance or force change, and therefore even a slight change in eitherof the input stream pressures effects a relatively substantial change inthe equilibrium position for the resultant stream. A unit scaled exactlyto the configuration illustrated in FIG. 1, when subjected to testsexhibited a pressure gain of the order of 6 (gain being defined aschanges of the differential pressure across output passages 23 and 27 asa function of changes in the differential pressure applied across inputnozzles 15 and 13). Higher order gains are achievable by varying theamplifer configuration, such as by decreasing the size of interactionchamber 17, changing the position and size of the outlet passage, etc.Gains on the order of those disclosed in the above-referenced Bjornsenpatent for the impact modulation should be achievable. Pressure recoveryin the unit tested was 66 percent. Since no power nozzle or associatedstructure was required, the unit is comparatively small.

A unit configured similar to that illustrated in FIG. 1, but havingprotrusion 31 removed was tested, with the result that gains were downby as much as one-half from the gain of the protrusion type unit, withpressure recovery and dynamic range suffering considerably.

It should be clear to those skilled in the art that the underlyingconcept of the present invention is suitable for constructionalarrangements which vary somewhat from that in FIG. 1. Specifically,asymmetrical configurations may be employed where the input signal fromeither of nozzles 13 and 15 is to be weighted. Examples of suchasymmetrical construction would be transverse displacement of protrusion31 along wall 19, rotational displacement of the various vent and outputpassages about protrusion 31, different sized input noules 13 and 15,etc. Furthermore, it should be clear that three-dimensionalconfigurations are possible wherein amplifier 10 may be considered asurface of revolution about its longitudinal center line or about anaxis perpendicular to the longitudinal centerline and displaced slightlybelow the wall 19 as viewed in FIG. 1, or other convenient axes.Further, any number of output passages may be provided in accordancewith the particular application in which the amplifier is to-beemployed.

In addition to its utilization as a proportional type amplifier, purefluid amplifier 10 of FIG. 1 may also be employed as a digital logicelement. Specifically, if bilevel, or binary fluid streams are appliedto the input ports or input nozzles 13 and 15, and protrusion 31 isconfigured to direct a stream issued from nozzle 13 away from wall 19and into output passage 27 and to direct a stream issued from nozzle 15away from wall 19 and into output passage 23, a multifunction logiccircuit is provided. The passages 23 and 27 may be connected to a commonpassage provided a signal representing the exclusive OR function, thatis a signal present when either, but not both, of

input passages 13 and 15 receive a binary-one input signal. When bothnozzles 13 and 15 receive binary one input signals the resultant streamis directed to center output passage 25 which thereby provides a signalrepresentative of the AND logic function. It will be evident to those-ofordinary-skill in the art that various other logic functions-may beprovided by units similar to pure fluid-amplifier 10 by simply providingappropriate output passages. interrelatedwith the directivity ofwedge-shaped protrusion 31. Similarly,-vent passages 21 and 29 may beremoved and replaced by appropriate sidewalls for region 17. This latterconfiguration permits boundary layer lock-on effects to be utilized toaccomplish logic functions in a manner similar to power stream-typedevices. 1

Referring now specifically to. FIG: 12, there is illustrated anotherembodiment of the present'inventiomA pair of input passages 53 and55'communicate with interaction chamber. or

region 57,'nozzles 53 and 55being substantially opposed at thedownstream endof chamber.57.- Communicating with interaction chamber 57in clockwise sequencefromnozzle 53 to nozzle 55' asviewed in FIG. 2 areventpassage 51, output passage 63, output passage 65, and input-passages67, 69, 71" and 72. The various passages sequentially recited areseparated by conventional wedge-shaped flow dividers having theirapices-bordering the interaction chamber 57. Flow divider 75, whichseparates output passages 63 and 65,has a generally semicircular recess77 formed. at its apex, recess 77 terminating at its extremities incusps 79 and 8l adjacent respective output passages 63 and 65. A furtherventing passage 83 communicates with output passage 65 downstream ofchamber 57 and a passage 85 communicates between vent passage 61 andoutput passage 63 downstream of chamber 57. A wedge-shaped protrusion 91extends from wall 59' into chamber 57 in a manneranalogous to theextension of protrusion 31 of the chamber 17 in FIG. 1. Input nozzles53' and 55 are connected to a common input passage 93.

Wedge-shaped protrusion-9l is in substantial alignment with cusp 81.When equal flow is provided. by nozzles 53 and 55 so that a resultantstream is produced normal .to "wall 59, the-main portion of theresultant stream is directed towards output passage 65. The leftmostportion of the resultant stream, however, as viewed in FIG. 2,;isscooped or peeled off by cusp 81 and diverted by semicircular recess 77.Someof the fluid thusly diverted is directed backlagainst the leftsideof the resultant stream to'further deflect'thestream into output.passage 65. Other portions of the diverted fluid are vented to ambientpressure via passages 61 and 85.

The egress orifices .of respective input passages are'directed to issuefluid streamsgenerally towardlto the. pivot ipoint'or point ofinteraction between the stream issued from nozzles 53: v and 55. This isdone to maximize the effects of the input control streams on thebalanced force resultant power stream and thereby enhance thesensitivity of amplifier 50. For someapplications of course the inputpassages may be otherwise directed. L v Y In operation input passage 93'is connected toa source of constant pressure fluid and if inputnozzles53and 55 are. identically configured and symmetrically disposedabout wedge-shaped protrusion 91, a resultant power stream flow isproduced which is directed towards output passage 65.-

If an input signal is received in the-form of a fluid control resultfrom the presence-of one or more input signals at input passages 67, 69,71 and .73. Thus, relatively low energy is required of the inputcontrolstreams from: these passages to produce deflection of the power stream.This. of course. increases the fan-out capabilities of thepreceeding'stages which produce these input signals.

The particular configuration for amplifier 50 illustrated in FIG. 2 isan OR/NOR gate having four inputs wherein a NOR output signal isprovided in passage 65 whenever none of the input passages 67, 69, 71,73 receive input signals and output passages 63 provides an OR outputsignal whenever an input control signal is provided by any of the inputpassages. Of course, by appropriately positioning the input and outputpassages various other configurations'utilizing the balanced force powerstream concept can be constructed by those skilled in theart so as toproduce desired logicfunctions. In addition, it is to be understood thatfor-certain applications the resultant power stream need not bequiescently directed perpendicular to wall 59; that is, in the absenceof control signals. it may be desirable to direct the power stream atsome angle other than 90 relative to wall 59. This may be readily accomvplished by displacing nozzles 53 and 55 asymmetrically with stream fromany of input passages 67,'.69, 71 or 73' the resultant power stream isdeflectedftowards outputpassage I 63. When so deflected, the right-handportion of the deflected stream, as viewed in FIG. 2, is scoopedorpeeledoff by cusp 79 and diverted by semicircular recess 77. A portionof the: diverted fluid acts against the right-hand portion of the.

deflected power stream to maintain the power stream directed" towardoutput passage 63; the remaining portion of the" diverted fluid isvented by meansof venting passage 83'com-- municating with outputpassage 65. v

Because the power stream of device 50 is the resultant in a balancedforce system, the angular position of the power stream is extremelysensitive to anyforce unbalance aswould respect to protrusion 91 or byproviding these nozzles'with unequal flow characteristics or bydirecting the cusp other than at relative to the wall 59.

Amplifier 50 of FIG. 2 may be converted to a proportional or analogueamplifier by replacing the semi'spherical recess 77 l and cusps 79and'8l with a conventional wedge shaped divider similar to thosedividingthe'otherpassages in-amplifier 50. As an analogue amplifier,amplifier 50 produces highly sensitive power stream deflection as afunction of an analogue pressure range has hamperedpriorart attempts atproviding:

purefluid analog-todigital converters. The utilization-of pure fluidamplifier 10. as a comparator has solved the prior art problems in thisregard. An analogue input pressure signal is provided. to a comparatorwhich may be similar or identi cal to fluid amplifier 10 of FIG. 1. Thepressure differential output signal of comparator 110" is .then appliedas ari'input signal to a digital signal generator 111. Digital signalgenerator Ill-may be'a conventional priorart device which'respondstopressuredifferential to provide. a proportional digital output signal.For example, digital signal generator 111 may comprise a pair ofpressurecontrol oscillators feeding a respective pair of spillovercounters; the input signals'to tlie pressure'co'm trolled oscillatorsbeing output passages 23 and 27'ofamplifier l0of FIG. 1, for example. Adigital register'for comparingthe' 1 counts in the. two counters maythen :be-employed to provide the digital output signal of thedevice'rAdigital signal 'genera-' tor such as this is disclosedv incopending patent applicatio'n U.S. Pat. Ser. No. 500,977 by EdwinMl-Dexter, entitl'ed- Vortex Readout System" andassigned-to the sameassignee-as the present invention. Thedigital outputsignal-from-generator 111 'is applied to a conventional digital toanalogue-converter unit: 113, the analogue output signal' from which isfed baclcas a further input signal to comparator 110':

'Control systemssuch as the one illustrated in FIG? 3'- are per seconventional. But prior 'to the present invention sensitivity operatingrange and a high sensitivity.

While we have described and illustrated several specific em 'bodimentsof our invention, it will be clear that'variation of the details ofconstruction which are specifically illustratedspirit and scope of theinverTo'nas defined in the appended claims.

I claim:

1. A pure fluid element comprising:

a wall;

means for establishing a pair of opposed input fluid streams along saidwall;

protruding means extending from said wall for deflecting said inputstreams away from said wall and into interacting relationship with oneanother to provide a resultant stream;

control means for varying the angular position of said resultant streamabout said protruding means; and

output means for receiving varying portions of said resultant stream asa function of its angular position.

2. The combination according to claim 1 wherein said control meansincludes means for varying the strength of at least one of said inputstreams.

3. The pure fluid element according to claim 2 wherein: said walldefines the upstream end of an interaction chamber; said means forestablishing comprises a pair of opposed nozzles for issuing said inputstreams; said protruding means comprises a substantially wedge-shapedmember extending from said wall into said interaction chamber; and saidoutput means comprises at least one fluid output passage communicatingwith said interaction chamber downstream of said opposed nozzles.

4. The pure fluid element according to claim 3 wherein saidsubstantially wedge-shaped member extends from said wall to a distancewhich is a smaller than the width of said opposed nozzles.

5. The pure fluid element according to claim 3 wherein said output meansfurther comprises another fluid output passage communicating with saidinteraction chamber downstream of said opposed nozzles, said one andanother fluid output passages providing an output pressure differentialas a function of the pressure differential across said opposed nozzles.

6. The pure fluid element according to claim 5 further comprising meansfor venting said interaction chamber to ambient pressure.

7. The pure fluid element according to claim 1 wherein said controlmeans includes'at least one control nozzle for selectively issuing acontrol stream in interacting relationship with said resultant stream.

8. The pure fluid element according to claim 7 wherein: said walldefines the upstream end of an interaction chamber; said means forestablishing comprises a pair of opposed nozzles connected to a commonsource of fluid pressure for issuing said input streams; said protrudingmeans comprises a substantially wedge-shaped member extending from saidwall into said interaction chamber; and said-control means comprises atleast one output passage communicating with said interaction chamberdownstream of said opposed nozzles.

9. The pure fluid element according to claim 8 wherein said output meansfurther comprises another output passage communicating with saidinteraction chamber, said one and said another output passages beingseparated by a flow divider having walls diverging outwardly from saidinteraction chamber, said flow divider having a concave region formed inthe end thereof facing said wall, said concave region defining a pair ofcusps adjacent a respective output passage, the cusps being directedtoward said wall and located such that a portion of the resultant streamreceived by each output passage is peeled off by a respective cusp anddiverted by said recess into interacting relation with the resultantstream.

10. The pure fluid element according to claim 1 wherein: said walldefines the upstream end of an interaction chamber; said means forestablishing comprises a pair of opposed nozzles for issuing said inputstreams; said protruding means comprises a substantially wedge-shapedmember extending from said wall into said interaction chamber; and saidoutput means comprises at least one fluid output passage communicatingwith said interaction chamber downstream of said opposed nozzles.

11. The pure fluid element according to claim 10 wherein said controlmeans includes means for varying the pressure in the region at whichsaid input fluid streams interact.

12. A fluidic element, comprising:

a wall having a surface;

means for establishing a pair of opposed fluid streams along saidsurface; and

reference-point means protruding from said surface for deflecting saidopposed fluid streams away from said surface and into interactingrelationship with one another to form a resultant fluid stream directedfrom said reference-point means at an angle relative to said surfacesaid angle being a function of the relative strengths of said opposedfluid streams.

13. The element according to claim 12 further comprising output meansfor receiving varying portions of said resultant fluid stream as afunction of the angle made by said resultant fluid stream relative tosaid surface.

14. The fluidic element according to claim 12 further comprising meansfor selectively varying the relative strengths of said opposed fluidstreams.

15. The fluidic element according to claim 12 wherein said protrudingmeans is a substantially wedge-shaped member having an apex extendingfrom said surface to a distance which is less than the transversedimension of either of said opposed fluid streams.

16. The fluidic element according to claim 12 further comprising controlmeans for selectively deflecting said resultant fluid stream.

17. The fluidic element according to claim 16 wherein said control meanscomprises means for issuing a control stream of fluid into interactingrelationship with said resultant fluid stream.

18. A fluidic element, comprising:

a wall having a surface;

means for establishing a pair of opposed fluid streams along saidsurface;

reference-point means protruding from said surface at a fixed locationrelative to the rest of said fluidic element for deflecting said opposedfluid streams away from said surface and into interacting relationshipwith one another to form a resultant fluid stream; and

output means for receiving varying portions of said resultant fluidstream as a function of the relative strengths of said opposed fluidstreams.

19. The element according to claim 18 further comprising means forselectively deflecting said resultant fluid stream.

20. The element according to claim 18 wherein: said surface defines theupstream end of an interaction region; said means for establishingcomprises a pair of nozzles arranged to issue respective ones of opposedstreams along said surface; and said output means includes at least onefluid passage having an ingress opening communicating with saidinteraction region downstream of said pair of nozzles.

1. A pure fluid element comprising: a wall; means for establishing apair of opposed input fluid streams along said wall; protruding meansextending from said wall for deflecting said input streams away fromsaid wall and into interacting relationship with one another to providea resultant stream; control means for varying the angular position ofsaid resultant stream about said protruding means; and output means forreceiving varying portions of said resultant stream as a function of itsangular position.
 2. The combination according to claim 1 wherein saidcontrol means includes means for varying the strength of at least one ofsaid input streams.
 3. The pure fluid element according to claim 2wherein: said wall defines the upstream end of an interaction chamber;said means for establishing comprises a pair of opposed nozzles forissuing said input streams; said protruding means comprises asubstantially wedge-shaped member extending from said wall into saidinteraction chamber; and said output means comprises at least one fluidoutput passage communicating with said interaction chamber downstream ofsaid opposed nozzles.
 4. The pure fluid element according to claim 3wherein said substantially wedge-shaped member extends from said wall toa distance which is a smaller than the width of said opposed nozzles. 5.The pure fluid element according to claim 3 wherein said output meansfurther comprises another fluid output passage communicating with saidinteraction chamber downstream of said opposed nozzles, said one andanother fluid output passages providing an output pressure differentialas a function of the pressure differential across said opposed nozzles.6. The pure fluid element according to claim 5 further comprising meansfor venting said interaction chamber to ambient pressure.
 7. The purefluid element according to claim 1 wherein said control means includesat least one control nozzle for selectively issuing a control stream ininteracting relationship with said resultant stream.
 8. The pure fluidelement according to claim 7 wherein: said wall defines the upstream endof an interaction chamber; said means for establishing comprises a pairof opposed nozzles connected to a common source of fluid pressure forissuing said input streams; said protruding means comprises asubstantially wedge-shaped member extending from said wall into saidinteraction chamber; and said control means comprises at least oneoutput passage communicating with said interaction chamber downstream ofsaid opposed nozzles.
 9. The pure fluid element according to claim 8wherein said output means further comprises another output passagecommunicating with said interaction chamber, said one and said anotheroutput passages being separated by a flow divider having walls divergingoutwardly from said interaction chamber, said flow divider having aconcave region formed in the end thereof facing said wall, said concaveregion defining a pair of cusps adjacent a respective output passage,the cusps being directed toward said wall and located such that aportion of the resultant stream received by each output passage ispeeled off by a respective cusp and diverted by said recess intointeracting relation with the resultant stream.
 10. The pure fluidelement according to claim 1 wherein: said wall defines the upstream endof an interaction chamber; said means for establishing comprises a pairof opposed nozzles for issuing said input streams; said protruding meanscomprises a substantially wedge-shaped member extending from said wallinto said interaction chamber; and said output means comprises at leastone fluid output passage communicating with said interaction chamberdownstream of said opposed nozzles.
 11. The pure fluid element accordingto claim 10 wherein said control means includes means for varying thepressure in the region at which said input fluid streams interact.
 12. Afluidic element, comprising: a wall having a surface; means forestablishing a pair of opposed fluid streams along said surface; andreference-point means protruding from said surface for deflecting saidopposed fluid streams away from said surface and into interactingrelationship with one another to form a resultant fluid stream directedfrom said reference-point means at an angle relative to said surfacesaid angle being a function of the relative strengths of said opposedfluid streams.
 13. The element according to claim 12 further comprisingoutput means for receiving varying portions of said resultant fluidstream as a function of the angle made by said resultant fluid streamrelative to said surface.
 14. The fluidic element according to claim 12further comprising means for selectively varying the relative strengthsof said opposed fluid streams.
 15. The fluidic element according toclaim 12 wherein said protruding means is a substantially wedge-shapedmember having an apex extending from said surface to a distance which isless than the transverse dimension of either of said opposed fluidstreams.
 16. The fluidic element according to claim 12 furthercomprising control means for selectively deflectiNg said resultant fluidstream.
 17. The fluidic element according to claim 16 wherein saidcontrol means comprises means for issuing a control stream of fluid intointeracting relationship with said resultant fluid stream.
 18. A fluidicelement, comprising: a wall having a surface; means for establishing apair of opposed fluid streams along said surface; reference-point meansprotruding from said surface at a fixed location relative to the rest ofsaid fluidic element for deflecting said opposed fluid streams away fromsaid surface and into interacting relationship with one another to forma resultant fluid stream; and output means for receiving varyingportions of said resultant fluid stream as a function of the relativestrengths of said opposed fluid streams.
 19. The element according toclaim 18 further comprising means for selectively deflecting saidresultant fluid stream.
 20. The element according to claim 18 wherein:said surface defines the upstream end of an interaction region; saidmeans for establishing comprises a pair of nozzles arranged to issuerespective ones of opposed streams along said surface; and said outputmeans includes at least one fluid passage having an ingress openingcommunicating with said interaction region downstream of said pair ofnozzles.